US4990468A - Fluorophosphate optical glass - Google Patents
Fluorophosphate optical glass Download PDFInfo
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- US4990468A US4990468A US07/414,385 US41438589A US4990468A US 4990468 A US4990468 A US 4990468A US 41438589 A US41438589 A US 41438589A US 4990468 A US4990468 A US 4990468A
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- United States
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- partial dispersion
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- baf
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- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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- 239000005304 optical glass Substances 0.000 title claims abstract description 20
- DWYMPOCYEZONEA-UHFFFAOYSA-L fluoridophosphate Chemical compound [O-]P([O-])(F)=O DWYMPOCYEZONEA-UHFFFAOYSA-L 0.000 title claims abstract description 12
- 239000006185 dispersion Substances 0.000 claims abstract description 35
- 229910001632 barium fluoride Inorganic materials 0.000 claims abstract description 12
- 239000000126 substance Substances 0.000 claims abstract description 12
- 239000000203 mixture Substances 0.000 claims abstract description 10
- 125000005341 metaphosphate group Chemical group 0.000 claims abstract description 8
- 150000002222 fluorine compounds Chemical class 0.000 claims abstract description 7
- 229910001404 rare earth metal oxide Inorganic materials 0.000 claims abstract description 4
- 229910052788 barium Inorganic materials 0.000 claims abstract description 3
- 229910052791 calcium Inorganic materials 0.000 claims abstract description 3
- 229910052749 magnesium Inorganic materials 0.000 claims abstract description 3
- 229910052712 strontium Inorganic materials 0.000 claims abstract description 3
- 239000011521 glass Substances 0.000 claims description 35
- 229910052688 Gadolinium Inorganic materials 0.000 claims description 2
- 229910052769 Ytterbium Inorganic materials 0.000 claims description 2
- 229910052746 lanthanum Inorganic materials 0.000 claims description 2
- 229910052727 yttrium Inorganic materials 0.000 claims description 2
- 230000002159 abnormal effect Effects 0.000 abstract description 13
- KLZUFWVZNOTSEM-UHFFFAOYSA-K Aluminium flouride Chemical compound F[Al](F)F KLZUFWVZNOTSEM-UHFFFAOYSA-K 0.000 abstract description 8
- 230000003287 optical effect Effects 0.000 abstract description 7
- 229910001637 strontium fluoride Inorganic materials 0.000 abstract description 7
- FVRNDBHWWSPNOM-UHFFFAOYSA-L strontium fluoride Chemical compound [F-].[F-].[Sr+2] FVRNDBHWWSPNOM-UHFFFAOYSA-L 0.000 abstract description 7
- 229910001635 magnesium fluoride Inorganic materials 0.000 abstract description 4
- 229910005693 GdF3 Inorganic materials 0.000 abstract description 3
- WUKWITHWXAAZEY-UHFFFAOYSA-L calcium difluoride Chemical compound [F-].[F-].[Ca+2] WUKWITHWXAAZEY-UHFFFAOYSA-L 0.000 abstract description 3
- 229910001634 calcium fluoride Inorganic materials 0.000 abstract description 3
- 230000000694 effects Effects 0.000 description 6
- QVQLCTNNEUAWMS-UHFFFAOYSA-N barium oxide Inorganic materials [Ba]=O QVQLCTNNEUAWMS-UHFFFAOYSA-N 0.000 description 5
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 4
- 239000002994 raw material Substances 0.000 description 4
- 238000002425 crystallisation Methods 0.000 description 3
- 230000008025 crystallization Effects 0.000 description 3
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 description 2
- 238000005266 casting Methods 0.000 description 2
- 239000005303 fluorophosphate glass Substances 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 238000002844 melting Methods 0.000 description 2
- 230000008018 melting Effects 0.000 description 2
- 238000002156 mixing Methods 0.000 description 2
- 229910052697 platinum Inorganic materials 0.000 description 2
- 239000007858 starting material Substances 0.000 description 2
- 229910019639 Nb2 O5 Inorganic materials 0.000 description 1
- 229910000147 aluminium phosphate Inorganic materials 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 235000011180 diphosphates Nutrition 0.000 description 1
- 238000010952 in-situ formation Methods 0.000 description 1
- 239000002198 insoluble material Substances 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000000155 melt Substances 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 229910052761 rare earth metal Inorganic materials 0.000 description 1
- 238000001228 spectrum Methods 0.000 description 1
- 230000000087 stabilizing effect Effects 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 238000005303 weighing Methods 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
- C03C3/00—Glass compositions
- C03C3/12—Silica-free oxide glass compositions
- C03C3/23—Silica-free oxide glass compositions containing halogen and at least one oxide, e.g. oxide of boron
- C03C3/247—Silica-free oxide glass compositions containing halogen and at least one oxide, e.g. oxide of boron containing fluorine and phosphorus
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10S501/00—Compositions: ceramic
- Y10S501/90—Optical glass, e.g. silent on refractive index and/or ABBE number
- Y10S501/902—Optical glass, e.g. silent on refractive index and/or ABBE number having ABBE number at least 70
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10S501/00—Compositions: ceramic
- Y10S501/90—Optical glass, e.g. silent on refractive index and/or ABBE number
- Y10S501/903—Optical glass, e.g. silent on refractive index and/or ABBE number having refractive index less than 1.8 and ABBE number less than 70
Definitions
- This invention relates to a fluorophosphate optical glass having optical constants, i.e. refractive index (nd) of 1.54 to 1.60 and Abbe number ( ⁇ d) of 68 to 75 and having abnormal partial dispersion represented by a relative partial dispersion of at least 0.537.
- An optical glass having abnormal partial dispersion, capable of effecting correction of the secondary spectrum in dispersing a lens, is very important for designing the same and is of high utility value.
- fluorophosphate glasses having abnormal partial dispersion and a refractive index (nd) of at most 1.50, a number of reports have been made and it is known that the fluorophosphate glass disclosed in Japanese Patent Laid-Open Publication No. 144141/1988 has been produced on a commercial scale and used for various optical instruments.
- optical designers have eagerly had requirements for an optical glass having a higher refractive index, lower dispersion and abnormal partial dispersion.
- the optical glasses having optical constants satisfying such requirements are known as disclosed in Japanese Patent Publication Nos. 28169/1978, 4145/1985 and 14500/1987.
- the known optical glasses contain large amounts of Ba(PO 3 ) 2 and BaO as essential components as in a glass composition, for example, comprising 2.0 to 13.0% of MgF 2 , 0 to 20.0% of SrF 2 1.0 to 33.0% of BaF 2 , 0 to 8.0% of AlF 3 , 0 to 8.0% of YF 3 , 13.0 to 39.0% of Al(PO 3 ) 3 , 0 to 24.0% of Mg(PO 3 ) 2 , 1.0 to 20.0% of Ca(PO 3 ) 2 , 5.0 to 19.0% of Ba(PO 3 ) 2 , 10.0 to 36.0% of BaO, 1.5 to 12.0% of Y 2 O 3 and/or Yb 2 O 3 , 0 to 6.0% of ZnO, 0 to 29.0% of PbO and 0 to 22.0% of Nb 2 O 5 , % being by weight, described in Japanese Patent Publication No.
- a chemical composition comprising 15 to 32% of Al(PO 3 ) 3 , 0 to 10% of Ba(PO 3 ) 2 , 0 to 10% of Sr(PO 3 ) 2 , 0 to 10% of Ca(PO 3 ) 2 and 0 to 10% of Mg(PO 3 ) 2 , the sum of the metaphosphates being 20 to 32%, 20 to 70% of BaF 2 , 5 to 40% of SrF 2 , 0 to 15% of CaF 2 , 0 to 10% of MgF 2 , 0 to 5% of AlF 3 and 0 to 5% of GdF 3 , the sum of the fluorides being 55 to 75%, and 5 to 22% of Gd 2 O 3 , 0 to 7% of La 3 O 3 , 0 to 10% of Y.sub. 2 O 3 and 0 to 10% of Yb 2 O 3 , the sum of the rare earth element oxides being 5 to 22%.
- an optical glass having a glass composition comprising Al(PO 3 ) 3 , BaF 2 , SrF 2 and Gd 2 O 3 as essential components has optical constants sought by the inventors.
- the present invention is based on this finding.
- the present invention provides a novel fluorophosphate optical glass having a refractive index of 1.54 to 1.60, an Abbe number of 68 to 75 and a relative partial dispersion of at least 0.537, which has a chemical composition (% by weight) comprising:
- Al(PO 3 ) 3 is a main component essential for forming the network structure of glass, contributing to stability and increasing the chemical durability, and is used in a proportion of 15 to 32%, since if less than 15%, not only the chemical durability is deteriorated but also the glass becomes unstable, while if more than 32%, crystallization tendency is too large to obtain the glass.
- Ba(PO 3 ) 2 , Sr(PO 3 ) 2 , Ca(PO 3 ) 2 and Mg(PO 3 ) 2 are optional components for raising the refractive index, increasing the chemical durability and improving the workability and are respectively used in a proportion of 0 to 10%, since if more than 10%, the abnormal partial dispersion is lowered. This should be avoided. If the sum of the amounts of these metaphosphates is less than 20% or more than 32%, the glass tends to be too crystallized to maintain it.
- BaF 2 is an essential component for lowering the dispersion and raising the abnormal partial dispersion and is used in a proportion of 20 to 70%, since if less than 20%, the glass tends to be crystallized, while if more than 70%, the chemical durability is deteriorated and the glass is too unstable to maintain it.
- SrF 2 is an essential component functioning similarly to BaF 2 and serving to stabilize the glass jointly with BaF 2 , and is used in a proportion of 5 to 40%, since if less than 5%, the stabilizing effect of glass is decreased, while if more than 40%, the chemical durability is deteriorated and the crystallization tendency is too increased to maintain it.
- CaF 2 is an optional component, although having the similar effect to BaF 2 and SrF 2 , and is used in a proportion of 0 to 15%, since if more than 15%, the glass tends to be crystallized and becomes unstable.
- MgF 2 is an optional component, although having the similar effect to BaF 2 and SrF 2 , and is used in a proportion of 0 to 10%, since if more than 10%, the glass tends to be crystallized and becomes unstable.
- AlF 3 is an optional component having an effect of lowering the dispersion and is used in a proportion of 0 to 5%, since if more than 5%, the glass tends to be too crystallized to maintain it.
- GdF 3 is an optional component having an effect of raising the refractive index without raising the dispersion, and an effect of increasing the hardness of the glass, and is used in proportion of 0 to 5%, since if more than 5%, the glass tends to be too crystallized to maintain it.
- the glass becomes unstable, while if more than 75%, not only the chemical durability is deteriorated but also the glass becomes unstable.
- Gd 2 O 3 is an essential component capable of raising the refractive index without raising the dispersion as well as imparting a high refractive index and abnormal partial dispersion without substantial introduction of barium oxide component, and further capable of raising the hardness of the glass and serving to improve the mechanical strength and workability. It is used in a proportion of 5 to 22%, since if less than 5%, the intended refractive index cannot be obtained and the mechanical strength and workability are deteriorated, while if more than 22%, dissolving of it is difficult and the insoluble material is precipitated, resulting in the crystallization tendency.
- La 2 O 3 , Y 2 O 3 and Yb 2 O 3 are optional components, although having the similar effect to Gd 2 O 3 , and are respectively used in a proportion of 0 to 7%, 0 to 10% and 0 to 10%, since if the amounts of La 2 O 3 , Y 2 O 3 and Yb 2 O 3 are respectively more than 7%, 10% and 10%, the glass tends to be too crystallized to maintain it.
- the intended refractive index cannot be obtained, while if more than 22%, dissolving of them is difficult and insoluble ones are precipitated, so that the glass tends to be too crystallized to maintain it.
- Production of the fluorophosphate optical glass of the present invention can generally be carried out by mixing raw materials in a predetermined proportion to give the above described composition, melting the mixture at a temperature of 1000° C. to 1250° C., and then subjecting the melt to casting in a conventional manner.
- the fluorophosphate optical glass of the present invention has optical constants, i.e. a refractive index (nd) of 1.54 to 1.60, an Abbe number ( ⁇ d) of 68 to 75 and abnormal partial dispersion represented by a relative partial dispersion of at least 0.537, is excellent in chemical durability as well as stability and can readily be produced on a commercial scale, as described above.
- glass composition of the present invention examples are shown in Table 1 and the refractive indexes (nd), Abbe numbers ( ⁇ d) and relative partial dispersion values (ng-nF/nF-nC) are shown in Table 2.
- the fluorophosphate optical glass of the present invention was prepared by weighing the corresponding metaphosphates, oxides and fluorides, as raw materials, in predetermined proportions, mixing adequately these materials to prepare a starting material for the glass preparation, charging the starting material in a platinum crucible, melting in an electric furnace at a temperature of 1000° to 1250° C., stirring by a platinum stirrer to render the material clear and homogeneous, casting in a suitably preheated metal mold and then cooling gradually.
- Example 1 for example, the raw materials corresponding to the composition of Example 1 were weighed and mixed adequately according the above described procedure and then melted in an electric furnace previously heated at 1100° C. for 3 hours, thus obtaining a fluorophosphate optical glass with a refractive index (nd) of 1.58222, an Abbe number ( ⁇ d) of 69.2 and a relative partial dispersion (ng-nF/nF-nC) of 0.545.
- nd refractive index
- ⁇ d Abbe number
- ng-nF/nF-nC relative partial dispersion
- metaphosphates were used, but the present invention should not be construed to be limited thereto and of course, other raw materials capable of in situ formation of the metaphosphates can be used, for example, oxides and phosphoric acid in combination, or pyrophosphates to give the specified quantity according to the present invention.
- oxides and phosphoric acid in combination or pyrophosphates to give the specified quantity according to the present invention.
- pyrophosphates to give the specified quantity according to the present invention.
- the above described fluorides can partly be replaced by several percents of LiF, NaF and/or KF as far as the object of the present invention is not lost.
- the relative partial dispersion (ng-nF/nF-nC) in Table 2 means the degree of abnormal partial dispersion that a glass has positioned apart from the straight line connecting two points of relative partial dispersion when taking the relative partial dispersion on the ordinate and the Abbe number ( ⁇ d) on the abscissa choosing normal glasses 511605-K7 and 620363-F2 as a standard. Since in the scope of the present invention as claimed, the standard relative partial dispersion of the normal glasses are 0.532 and 0.521 respectively at an Abbe number ( ⁇ d) of 68 and 75, a glass has abnormal partial dispersion if the relative partial dispersion of this glass is apart from the straight line connecting two points of the standard relative partial dispersion.
- the glass of Example 1 has abnormal partial dispersion in view of its large relative partial dispersion (ng-nF/nF-nC), i.e. 0.545.
- the glasses of Examples 1 to 20 according to the present invention show higher refractive indexes (nd) and larger relative partial dispersion (ng-nF/nF-nC).
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- Chemical & Material Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Chemical & Material Sciences (AREA)
- Geochemistry & Mineralogy (AREA)
- Materials Engineering (AREA)
- Organic Chemistry (AREA)
- Glass Compositions (AREA)
Abstract
A fluorophosphate optical glass having optical constants, i.e. refractive index (nd) of 1.54 to 1.60 and Abbe number (νd) of 68 to 75 and having abnormal partial dispersion represented by a relative partial dispersion of at least 0.537 is provided, which has a chemical composition (% by weight) comprising:
______________________________________
Al(PO3)3 15-32%
Ba(PO3)2 0-10%
Sr(PO3)2 0-10%
Ca(PO3)2 0-10%
Mg(PO3)2 0-10%
sum of metaphosphates
20-32%
BaF2 20-70%
SrF2 5-40%
CaF2 0-15%
MgF2 0-10%
AlF3 0-5%
GdF3 0-5%
sum of fluorides 55-75%
Gd2 O3 5-22%
La2 O3 0-7%
Y2 O3 0-10%
Yb2 O3 0-10%
sum of rare earth oxides
5-22%
______________________________________
Description
1. Field of the Invention
This invention relates to a fluorophosphate optical glass having optical constants, i.e. refractive index (nd) of 1.54 to 1.60 and Abbe number (νd) of 68 to 75 and having abnormal partial dispersion represented by a relative partial dispersion of at least 0.537.
2. Description of the Prior Art
An optical glass having abnormal partial dispersion, capable of effecting correction of the secondary spectrum in dispersing a lens, is very important for designing the same and is of high utility value.
As to fluorophosphate glasses having abnormal partial dispersion and a refractive index (nd) of at most 1.50, a number of reports have been made and it is known that the fluorophosphate glass disclosed in Japanese Patent Laid-Open Publication No. 144141/1988 has been produced on a commercial scale and used for various optical instruments.
On the other hand, optical designers have eagerly had requirements for an optical glass having a higher refractive index, lower dispersion and abnormal partial dispersion. The optical glasses having optical constants satisfying such requirements are known as disclosed in Japanese Patent Publication Nos. 28169/1978, 4145/1985 and 14500/1987.
The known optical glasses contain large amounts of Ba(PO3)2 and BaO as essential components as in a glass composition, for example, comprising 2.0 to 13.0% of MgF2, 0 to 20.0% of SrF2 1.0 to 33.0% of BaF2, 0 to 8.0% of AlF3, 0 to 8.0% of YF3, 13.0 to 39.0% of Al(PO3)3, 0 to 24.0% of Mg(PO3)2, 1.0 to 20.0% of Ca(PO3)2, 5.0 to 19.0% of Ba(PO3)2, 10.0 to 36.0% of BaO, 1.5 to 12.0% of Y2 O3 and/or Yb2 O3, 0 to 6.0% of ZnO, 0 to 29.0% of PbO and 0 to 22.0% of Nb2 O5, % being by weight, described in Japanese Patent Publication No. 4145/1985. However, the large contents of Ba(PO3)2 and BaO result in not only increase of the dispersion but also lowering of the abnormal partial dispersion. These known optical glasses having a relatively high liquidus temperature are so unstable that crystals tend to be precipitated and comparable properties to those of the optical glass according to the present invention cannot be realized in a stable manner.
It is an object of the present invention to provide a fluorophosphate optical glass having a refractive index (nd) of 1.54 to 1.60, an Abbe number (νd) of 68 to 75 and a relative partial dispersion of at least 0.537.
It is another object of the present invention to provide a stable fluorophosphate optical glass having an excellent chemical durability, which can be produced on a commercial scale.
These objects can be attained by a chemical composition (% by weight) comprising 15 to 32% of Al(PO3)3, 0 to 10% of Ba(PO3)2, 0 to 10% of Sr(PO3)2, 0 to 10% of Ca(PO3)2 and 0 to 10% of Mg(PO3)2, the sum of the metaphosphates being 20 to 32%, 20 to 70% of BaF2, 5 to 40% of SrF2, 0 to 15% of CaF2, 0 to 10% of MgF2, 0 to 5% of AlF3 and 0 to 5% of GdF3, the sum of the fluorides being 55 to 75%, and 5 to 22% of Gd2 O3, 0 to 7% of La3 O3, 0 to 10% of Y.sub. 2 O3 and 0 to 10% of Yb2 O3, the sum of the rare earth element oxides being 5 to 22%.
The inventors have made various efforts to overcome the disadvantages of the prior art fluorophosphate optical glasses, as described above, and consequently, have found that an optical glass having a glass composition comprising Al(PO3)3, BaF2, SrF2 and Gd2 O3 as essential components has optical constants sought by the inventors. The present invention is based on this finding.
Accordingly, the present invention provides a novel fluorophosphate optical glass having a refractive index of 1.54 to 1.60, an Abbe number of 68 to 75 and a relative partial dispersion of at least 0.537, which has a chemical composition (% by weight) comprising:
______________________________________
Al(PO.sub.3).sub.3
15-32%, preferably 20-27%
Ba(PO.sub.3).sub.2
0-10%
Sr(PO.sub.3).sub.2
0-10%
Ca(PO.sub.3).sub.2
0-10%
Mg(PO.sub.3).sub.2
0-10%
sum of metaphosphates
20-32%
BaF.sub.2 20-70%, preferably 30-45%
SrF.sub.2 5-40%, preferably 15-30%
CaF.sub.2 0-15%
MgF.sub.2 0-10%
AlF.sub.3 0-5%
GdF.sub.3 0-5%
sum of fluorides 55-75%
Gd.sub.2 O.sub.3 5-22%, preferably 10-20%
La.sub.2 O.sub.3 0-7%
Y.sub.2 O.sub.3 0-10%
Yb.sub.2 O.sub.3 0-10%
sum of rare earth oxides
5-22%.
______________________________________
The grounds for limiting the proportion ranges of the components to the foregoing are as follows:
Al(PO3)3 is a main component essential for forming the network structure of glass, contributing to stability and increasing the chemical durability, and is used in a proportion of 15 to 32%, since if less than 15%, not only the chemical durability is deteriorated but also the glass becomes unstable, while if more than 32%, crystallization tendency is too large to obtain the glass.
Ba(PO3)2, Sr(PO3)2, Ca(PO3)2 and Mg(PO3)2 are optional components for raising the refractive index, increasing the chemical durability and improving the workability and are respectively used in a proportion of 0 to 10%, since if more than 10%, the abnormal partial dispersion is lowered. This should be avoided. If the sum of the amounts of these metaphosphates is less than 20% or more than 32%, the glass tends to be too crystallized to maintain it.
BaF2 is an essential component for lowering the dispersion and raising the abnormal partial dispersion and is used in a proportion of 20 to 70%, since if less than 20%, the glass tends to be crystallized, while if more than 70%, the chemical durability is deteriorated and the glass is too unstable to maintain it.
SrF2 is an essential component functioning similarly to BaF2 and serving to stabilize the glass jointly with BaF2, and is used in a proportion of 5 to 40%, since if less than 5%, the stabilizing effect of glass is decreased, while if more than 40%, the chemical durability is deteriorated and the crystallization tendency is too increased to maintain it.
CaF2 is an optional component, although having the similar effect to BaF2 and SrF2, and is used in a proportion of 0 to 15%, since if more than 15%, the glass tends to be crystallized and becomes unstable.
MgF2 is an optional component, although having the similar effect to BaF2 and SrF2, and is used in a proportion of 0 to 10%, since if more than 10%, the glass tends to be crystallized and becomes unstable.
AlF3 is an optional component having an effect of lowering the dispersion and is used in a proportion of 0 to 5%, since if more than 5%, the glass tends to be too crystallized to maintain it.
GdF3 is an optional component having an effect of raising the refractive index without raising the dispersion, and an effect of increasing the hardness of the glass, and is used in proportion of 0 to 5%, since if more than 5%, the glass tends to be too crystallized to maintain it.
If the sum of the amounts of these fluorides is less than 55%, the glass becomes unstable, while if more than 75%, not only the chemical durability is deteriorated but also the glass becomes unstable.
Gd2 O3 is an essential component capable of raising the refractive index without raising the dispersion as well as imparting a high refractive index and abnormal partial dispersion without substantial introduction of barium oxide component, and further capable of raising the hardness of the glass and serving to improve the mechanical strength and workability. It is used in a proportion of 5 to 22%, since if less than 5%, the intended refractive index cannot be obtained and the mechanical strength and workability are deteriorated, while if more than 22%, dissolving of it is difficult and the insoluble material is precipitated, resulting in the crystallization tendency.
La2 O3, Y2 O3 and Yb2 O3 are optional components, although having the similar effect to Gd2 O3, and are respectively used in a proportion of 0 to 7%, 0 to 10% and 0 to 10%, since if the amounts of La2 O3, Y2 O3 and Yb2 O3 are respectively more than 7%, 10% and 10%, the glass tends to be too crystallized to maintain it.
If the sum of the amounts of these rare earth oxides is less than 5%, the intended refractive index cannot be obtained, while if more than 22%, dissolving of them is difficult and insoluble ones are precipitated, so that the glass tends to be too crystallized to maintain it.
Production of the fluorophosphate optical glass of the present invention can generally be carried out by mixing raw materials in a predetermined proportion to give the above described composition, melting the mixture at a temperature of 1000° C. to 1250° C., and then subjecting the melt to casting in a conventional manner.
The fluorophosphate optical glass of the present invention has optical constants, i.e. a refractive index (nd) of 1.54 to 1.60, an Abbe number (νd) of 68 to 75 and abnormal partial dispersion represented by a relative partial dispersion of at least 0.537, is excellent in chemical durability as well as stability and can readily be produced on a commercial scale, as described above.
The following examples are given in order to illustrate the present invention in greater detail without limiting the same.
Examples of the glass composition of the present invention are shown in Table 1 and the refractive indexes (nd), Abbe numbers (νd) and relative partial dispersion values (ng-nF/nF-nC) are shown in Table 2.
The fluorophosphate optical glass of the present invention was prepared by weighing the corresponding metaphosphates, oxides and fluorides, as raw materials, in predetermined proportions, mixing adequately these materials to prepare a starting material for the glass preparation, charging the starting material in a platinum crucible, melting in an electric furnace at a temperature of 1000° to 1250° C., stirring by a platinum stirrer to render the material clear and homogeneous, casting in a suitably preheated metal mold and then cooling gradually.
In Example 1, for example, the raw materials corresponding to the composition of Example 1 were weighed and mixed adequately according the above described procedure and then melted in an electric furnace previously heated at 1100° C. for 3 hours, thus obtaining a fluorophosphate optical glass with a refractive index (nd) of 1.58222, an Abbe number (νd) of 69.2 and a relative partial dispersion (ng-nF/nF-nC) of 0.545.
In these examples, the metaphosphates were used, but the present invention should not be construed to be limited thereto and of course, other raw materials capable of in situ formation of the metaphosphates can be used, for example, oxides and phosphoric acid in combination, or pyrophosphates to give the specified quantity according to the present invention. The above described fluorides can partly be replaced by several percents of LiF, NaF and/or KF as far as the object of the present invention is not lost.
The relative partial dispersion (ng-nF/nF-nC) in Table 2 means the degree of abnormal partial dispersion that a glass has positioned apart from the straight line connecting two points of relative partial dispersion when taking the relative partial dispersion on the ordinate and the Abbe number (νd) on the abscissa choosing normal glasses 511605-K7 and 620363-F2 as a standard. Since in the scope of the present invention as claimed, the standard relative partial dispersion of the normal glasses are 0.532 and 0.521 respectively at an Abbe number (νd) of 68 and 75, a glass has abnormal partial dispersion if the relative partial dispersion of this glass is apart from the straight line connecting two points of the standard relative partial dispersion.
As apparent from the results of Examples, for example, the glass of Example 1 has abnormal partial dispersion in view of its large relative partial dispersion (ng-nF/nF-nC), i.e. 0.545.
In comparison with the prior art optical glasses having an Abbe number (νd) of 66 to 70 shown in Table 3, the glasses of Examples 1 to 20 according to the present invention show higher refractive indexes (nd) and larger relative partial dispersion (ng-nF/nF-nC).
TABLE 1
__________________________________________________________________________
1 2 3 4 5 6 7 8 9 10
__________________________________________________________________________
Al(PO.sub.3).sub.3
25.0
20.0
25.0
30.0
30.0
20.0
20.0
17.0
25.0
25.0
Ba(PO.sub.3).sub.2 10.0
Sr(PO.sub.3).sub.2
Ca(PO.sub.3).sub.2
Mg(PO.sub.3).sub.2
BaF.sub.2
25.0
70.0
30.0
30.0
45.0
40.0
35.0
22.0
35.0
37.0
SrF.sub.2
30.0
5.0
30.0
30.0
20.0
20.0
20.0
13.0
25.0
23.0
CaF.sub.2 15.0
MgF.sub.2 8.0
AlF.sub.3 5.0
GdF.sub.3 5.0
Gd.sub.2 O.sub.3
20.0
5.0
15.0
10.0
5.0
15.0
20.0
15.0
5.0
10.0
La.sub.2 O.sub.3 5.0
Y.sub.2 O.sub.3
Yb.sub.2 O.sub.3 10.0
__________________________________________________________________________
11 12 13 14 15 16 17 18 19 20
__________________________________________________________________________
Al(PO.sub.3).sub.3
25.0
17.6
25.0
25.0
20.0
30.0
17.0
30.0
18.6
24.0
Ba(PO.sub.3).sub.2
Sr(PO.sub.3).sub.2
8.0
Ca(PO.sub.3).sub.2 8.0
Mg(PO.sub.3).sub.2 10.0
BaF.sub.2
33.0
25.6
25.0
37.0
60.0
60.0
22.0
35.0
25.8
41.0
SrF.sub.2
27.0
14.4
40.0
23.0
5.0
5.0
13.0
20.0
14.4
20.0
CaF.sub.2 12.0 15.0 12.0
MgF.sub.2 6.4 8.0 6.4
AlF.sub.3
GdF.sub.3 1.0
Gd.sub.2 O.sub.3
5.0
15.0
10.0
8.0
15.0
5.0
15.0
15.0
15.0
8.0
La.sub.2 O.sub.3
2.0 2.0
Y.sub.2 O.sub.3
10.0 2.0
Yb.sub.2 O.sub.3
5.0 3.0
__________________________________________________________________________
TABLE 2
__________________________________________________________________________
1 2 3 4 5 6 7 8 9 10
__________________________________________________________________________
nd 1.58222
1.55697
1.56959
1.57030
1.56637
1.56879
1.58242
1.54874
1.57211
1.57484
νd
69.2 71.4 70.0 74.8 73.3 71.5 70.0 71.6 70.1 70.2
ng-nF/
0.545
0.544
0.544
0.543
0.543
0.550
0.539
0.545
0.545
nF-nC
__________________________________________________________________________
11 12 13 14 15 16 17 18 19 20
__________________________________________________________________________
nd 1.57474
1.55275
1.55302
1.57393
1.57944
1.57467
1.54122
1.58590
1.54708
1.57274
νd
70.7 71.6 69.0 68.2 69.1 69.0 74.9 69.3 74.1 71.5
ng-nF/
0.545
0.538
0.540
0.543
0.546
0.544
0.542
0.542
0.542
0.545
nF-nC
__________________________________________________________________________
TABLE 3
______________________________________
Glass
type 517696 487702 504668 716474 465659
______________________________________
nd 1.51728 1.48749 1.50378 1.47069
1.46450
νd 69.6 70.2 66.8 67.4 65.9
ng-nF/
0.532 0.530 0.531 0.534 0.533
nF-nC
______________________________________
Claims (6)
1. A fluorophosphate optical glass having a refractive index (nd) of 1.54 to 1.60, an Abbe number (νd) of 68 to 75 and a relative partial dispersion of at least 0.537, which has a chemical composition (% by weight) comprising:
______________________________________
Al(PO.sub.3).sub.3 15-32%
Ba(PO.sub.3).sub.2 0-10%
Sr(PO.sub.3).sub.2 0-10%
Ca(PO.sub.3).sub.2 0-10%
Mg(PO.sub.3).sub.2 0-10%
sum of metaphosphates
20-32%
BaF.sub.2 20-70%
SrF.sub.2 5-40%
CaF.sub.2 0-15%
MgF.sub.2 0-10%
AlF.sub.3 0-5%
GdF.sub.3 0-5%
sum of fluorides 55-75%
Gd.sub.2 O.sub.3 5-22%
La.sub.2 O.sub.3 0-7%
Y.sub.2 O.sub.3 0-10%
Yb.sub.2 O.sub.3 0-10%
sum of rare earth oxides
5-22%
______________________________________
2. The glass according to claim 1, containing 15-27 weight % of Al(PO3)3.
3. The glass according to claim 1, containing 20-27 weight % of Al(PO3)3.
4. The glass according to claim 1, containing 30-70 weight % of BaF2.
5. The glass according to claim 1, containing 30-45 weight % of BaF2.
6. The glass according to claim 2, containing 30-70 weight % of BaF2.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP63252350A JPH02124740A (en) | 1988-10-06 | 1988-10-06 | Optical fluorophosphate glass |
| JP63-252350 | 1988-10-06 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| US4990468A true US4990468A (en) | 1991-02-05 |
Family
ID=17236065
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| US07/414,385 Expired - Lifetime US4990468A (en) | 1988-10-06 | 1989-09-29 | Fluorophosphate optical glass |
Country Status (4)
| Country | Link |
|---|---|
| US (1) | US4990468A (en) |
| EP (1) | EP0364150B1 (en) |
| JP (1) | JPH02124740A (en) |
| DE (1) | DE68903825T2 (en) |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB649512A (en) * | 1946-01-29 | 1951-01-31 | Kodak Ltd | Improvements in and relating to optical glass |
| GB1136658A (en) * | 1965-12-31 | 1968-12-11 | Leitz Ernst Gmbh | Fluorophosphate glasses |
| US4358543A (en) * | 1979-10-04 | 1982-11-09 | Kabushika Kaisha Ohara Kogaku Garasu Seizosho | Fluoride glass |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3634675A1 (en) * | 1985-10-19 | 1987-04-23 | Leitz Ernst Gmbh | OPTICAL PHOSPHATE GLASS WITH ANOMAL POSITIVE PARTIAL DISPERSION AND METHOD FOR THE PRODUCTION THEREOF |
-
1988
- 1988-10-06 JP JP63252350A patent/JPH02124740A/en active Granted
-
1989
- 1989-09-29 US US07/414,385 patent/US4990468A/en not_active Expired - Lifetime
- 1989-10-03 EP EP89310118A patent/EP0364150B1/en not_active Expired
- 1989-10-03 DE DE8989310118T patent/DE68903825T2/en not_active Expired - Lifetime
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB649512A (en) * | 1946-01-29 | 1951-01-31 | Kodak Ltd | Improvements in and relating to optical glass |
| GB1136658A (en) * | 1965-12-31 | 1968-12-11 | Leitz Ernst Gmbh | Fluorophosphate glasses |
| US4358543A (en) * | 1979-10-04 | 1982-11-09 | Kabushika Kaisha Ohara Kogaku Garasu Seizosho | Fluoride glass |
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Also Published As
| Publication number | Publication date |
|---|---|
| EP0364150B1 (en) | 1992-12-09 |
| DE68903825D1 (en) | 1993-01-21 |
| EP0364150A1 (en) | 1990-04-18 |
| JPH0443854B2 (en) | 1992-07-17 |
| JPH02124740A (en) | 1990-05-14 |
| DE68903825T2 (en) | 1993-04-08 |
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